Intermodulation or intermodulation distortion (IMD) is the amplitude modulation of signals containing two or more different frequencies in a system with nonlinearities. For example, when two or more frequencies are passed through an amplifier, non-linearities in the amplifier result in distortion and cause the production of secondary signals that were not originally present. These secondary signals, or intermods as they are known, can interfere with receivers if they happen to coincide with the reception bands of any receivers in the vicinity. The intermodulation between each frequency component will form secondary signals at frequencies that are not just at harmonic frequencies (integer multiples) of either, but also at the sum and difference frequencies of the original frequencies and at multiples of those sum and difference frequencies.